Well, one advantage we have over commercial social media is that they need to pay people to write code and maintain the infrastructure, but a lot of work on Lemmy is volunteer-based.

Many admins for bigger instances are basically on-call the whole year for free, open source contributors provide code for free, etc. Even the core maintainers are effectively losing money by working on Lemmy, because while they are getting some income, the sum of money they are getting from working on Lemmy is way smaller than what they would get if they worked typical software engineering jobs.

Basically, if any non-volunteer organization wanted to replicate Lemmy, it would cost them quite a bit more in terms of payroll alone.

Another aspect is scale - Lemmy is able to spread the costs between different instances, and while growth of the network can generally increase costs for individual nodes, they will still end up paying less compared to if they were hosting the entire social network in a centralized way.